Polymers can think: how to create an artificial brain out of plastic
A new type of polymer mimics the work of biological neurons and can process information and learn.
Researchers from Osaka University and Hokkaido University developed a new type of polymer that can mimic how biological neurons work. These polymers are able to change their structure and conductivity depending on external stimuli such as electrical voltage or light. Thus, they can learn and remember information like living cells.
Polymeric brains are thin films of special organic compounds that have the property of shape memory. This means that they can retain their shape after being deformed and return to their original state when heated or lit. In addition, these polymers are electroactive, meaning they can change their electrical conductivity in response to an applied voltage.
The researchers were able to grow polymer wires from a common polymer blend called PEDOT:PSS, which is highly conductive, transparent, flexible and stable. The three-dimensional structure of the top and bottom electrodes was first immersed in the precursor solution. PEDOT:PSS wires were then grown between selected electrodes by applying a square wave voltage to these electrodes, mimicking the formation of synaptic connections by guiding axons in the immature brain.
Once the wire was formed, its characteristics, especially conductivity, were controlled by small voltage pulses applied to one electrode, which changes the electrical properties of the film surrounding the wires.
Polymeric brains have a number of advantages over traditional electronic neural networks. They are more flexible, lighter and cheaper to manufacture. They also consume less power and have a higher information density. In addition, they are closer to natural systems in their principle of operation and ability to self-organize.
The fabricated network was used to demonstrate unsupervised Hebbian learning (i.e., when synapses that often fire together strengthen their common bond over time). What’s more, the researchers were able to precisely control the conductance values of the wires so that the network could perform its tasks.
Spike-based learning, another approach to neural networks that more closely mimics the processes of biological neural networks, has also been demonstrated by controlling the diameter and conductance of wires.
Then, having made a chip with a large number electrodes and by using microfluidic channels to feed stock solution to each electrode, the researchers hope to build a larger and more powerful network. Overall, the approach defined in this study is a big step towards the implementation of neuromorphic software and bridging the gap between human and computer cognitive abilities.
Polymer brains can find applications in various fields such as biomedicine, robotics, artificial intelligence and the internet of things. They can be used to create smart prostheses, sensors, communication and memory devices. They can also help in studying the mechanisms of learning and memory in living organisms.